Amplifier device



Y 1939- R. URTEL- 2,156,659

AMPLIFIER DEVICE Filed June 17, 1936 lNVENTOR R. URTEL ATTORNEY Patented May 2, 1939 UNITED STATES AIIIPLIFIER DEVICE Rudolf Urtel, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. H., Berlin, Germany, a corporation of Germany Application June 17; 1936, Serial No. 85,648

In Germany April 1, 1935 1 Claim.

This invention relates to a circuit arrangement for amplifier tubes in which the plate currents of two tubes fiow through a joint external impedance or resistance in opposite directions.

A further object of the invention is to provide 5 an amplifier device consisting of two electron discharge tubes in which substantially no direct current flows through the load or output circuit but in which the alternating potentials produced by the separate tubes are added together.

For a better understanding of the invention reference is made to the accompanying drawing in which,

Figs. 1 and 2 are schematic circuit diagrams of amplifiers embodying the invention.

Referring to Fig. 1, I and II denote two amplifier tubes whose grids are connected with the secondary windings I2 and I3 of a transformer I4. The primary winding I5 of the said transformer is fed with the alternating potential to be amplified. Inside the circuit A, B, C, D, the two amplifiers transmitting current in the same sense are connected in series together with two sources of direct current I6 and II. The external impedance I8 which may consist of the primary winding of an output transformer I9 or else consist directly of the consumer or load to be supplied with current, is connected in parallel to each of the two tubes.

An examination of Fig. 1 will showthat the plate currents of the two tubes traverse the external resistance I8 in contrary directions seeing that the electron current of tube I0 flows from top to bottom, and that of tube II from below in an upward direction, across the external impedance I8. The secondary windings I2, I3, of transformer I4 are associated with the grids of both tubes in such manner that these two grids are operated in phase opposition (push-pull) In other words, if on the grid of tube Ill an alternation of the alternating voltage to be amplified is impressed in the positive sense so that the plate current of this tube is increased, then at the grid of tube II a potential of the alternation in question of a negative sense will arise so that the plate current of this tube is diminished. In the external impedance I8, as will thus be seen, the plate direct currents of the tubes are subtracted from each other, whereas the alternating plate potentials are added. It will be most advantageous to use two tubes having like characteristics, and to operate the tubes about the middles of their characteristics. The direct plate currents will then be completely balanced out.

55 In the exemplified embodiment of Fig. 2, the

plate circuit of tube I0 contains in addition a resistance 20 the left-hand end of which is united with the grid of tube II. The alternating voltage to be amplified is fed only to the grid of tube Ill.

Also this circuit organization operates with potentials in phase opposition at the two grids of the tubes inasmuch as the plate alternating current of tube III which, as known, is in phase opposition to the grid alternating potential of tube I0, forms at the same time the grid alternating voltage for the tube II. Hence, also in the case of the circuit shown in Fig. 2, the direct plate currents act in opposition in the external impedance I 8 so much so that, under certain circumstances, they will totally neutralize each other, whereas the alternating plate currents become added.

The new circuit arrangements hereinbefore disclosed have the property that they may be fed with a single-phase alternating potential, and that they will furnish an amplified single-phase current in spite of the fact that the amplification is brought about in two tubes. It is this fact that distinguishes the present scheme advantageously from the conventional types of push-pull amplifier arrangement.

It is moreover worth noting that the plate-current variations at the rate or rhythm of such harmonics of the voltages I6, II, as may be present will not be produced at all. On the contrary, these plate-current variations are neutralized just as the direct plate currents themselves are neutralized.

The new circuits here disclosed are particularly suited for the amplification of saw-tooth currents fed to the deflector coils of Braun or cathoderay tubes. It will be noted that in the case of curve-shapes of the said sort all frequencies as may be contained in the saw-tooth curve form must be amplified with fidelity (without distortion) both as regards amplitude and phase, a task which is attainable by other ways and means only at considerable cost.

Having described my invention, what I claim as novel and desire to secure by Letters Patent is:

In an amplifying device, the combination of two electron discharge tubes each having a cathode, a control grid and a plate, a conductor directly connecting the cathode of the first of said tubes to the plate of the second tube, a source of positive potential connected between the cathode of the second tube and the plate of the first tube, an output circuit connecting said directly connecting conductor to an intermediate point of said potential source, and an input transformer having a pair of secondary windings, each of which is connected between the control grid and cathode of one of said tubes, said windings causing the voltage of said control grids to vary in substantially opposite phase.

RUDOLF URTEL. 

